This invention relates to a motor for driving a propeller which includes a phase adjuster for changing the pitch of the propeller blades of the propeller.
Generally motors, and in particularly outboard motors for use with boats, include a drive shaft for transmitting rotary power to a propeller for rotating the propeller to drive the boat through the water. The propeller includes propeller blades which are angled to provide propulsion through the water. The angle or pitch of the blades relative to a radial axis transverse to the drive axis of the drive shaft is generally fixed and selected to provide maximum efficiency at maximum speed or cruise speed of the boat to which the motor is to be used. The pitch is generally less efficient at take-off when the boat is driven from stationary up to the cruise speed, which inefficiency results in increased fuel consumption and a longer time for the boat to move from the stationary to cruise speed.
The object of this invention is to provide a motor which overcomes these problems.
The invention may be said to reside in a motor for driving a propeller having a plurality of propeller blades, including:
a first output shaft having a drive axis for driving the propeller around the drive axis;
a second output shaft having a drive axis;
coupling means for coupling the second output shaft to each propeller blade of the propeller for rotating the propeller blades about a radial axis transverse to the drive axes of the first and second output shafts to change the pitch of the propeller blades relative to the radial axis;
an input for supplying input rotary power to the first and second output shafts for driving the first and second output shafts about the drive axes to transmit rotary power to the propeller; and
phase adjusting means for adjusting the phase relationship between the first and second output shafts so that one of the output shafts rotates relative to the other of the output shafts with the relative rotation causing the coupling means to rotate the propeller blades about the radial axis to change the pitch of the blades relative to the radial axis.
The phase adjusting means allows the pitch of the propeller blades to be altered so the pitch can be set at an optimum position for maximum efficiency at take-off of the vessel as the vessel moves from a stationary position and readjusted to provide maximum efficiency at cruise speed. Thus, an optimum pitch of the propeller blades can be selected depending on the conditions of the motor and speed of travel of the vessel to which the motor is coupled. This increases efficiency of the motor and decreases fuel consumption.
Preferably the coupling means comprises a bevel gear on the second output shaft which meshes with a bevel gear coupled to each propeller blade for rotating the propeller blades about the radial axis.
Preferably the propeller blades are each provided on a blade mounting, the blade mounting being coupled to the first output shaft for rotation with the first output shaft about the drive axis so that when the first and second output shafts rotate at the same speed drive is not transmitted from the first bevel gear on the second output shaft to the bevel gear on the mounting, but when relative rotation takes place between the first and second output shafts drive is transmitted from the bevel gear connected to the second output shaft to the bevel gear on the mounting to cause the mounting to rotate about the radial axis to alter the pitch of the propeller blade.
Preferably the phase adjusting means comprises:
a cage coupled to the input via the first and second output shafts and the input for input of rotary power;
a first gear on the first output shaft;
a second gear on the second output shaft;
a first planet gear in meshing engagement with the first gear on the first output shaft;
a second planet gear in meshing engagement with the second gear on the second output shaft;
a first orbit gear arranged for rotation relative to the first and second outputs and meshing with the first planet gear and a second output gear arranged for rotation relative to the outputs and engaging the second planet gear, one of the first or second orbit gears being fixed and the other of the first or second orbit gears being movable relative to the said one of the orbit gears; and
adjusting means for moving the movable orbit gear to cause the planet gear associated with that orbit gear to advance or regress relative to the other planet gear to thereby change the phase relationship between the first and second output shafts and to alter the pitch of the propeller blades via the coupling means which couples the second output shaft to each propeller blade.
In the preferred embodiment of the invention, the phase adjusting means includes a plurality of gears as described above. The geared arrangement of the phase adjusting means and the geared coupling of the second shaft to the propeller blades inherently allows for some backlash in the gear train which may be undesirable. The backlash in the train can, depending on the position of the propeller blades, cause the propeller blades to oscillate slightly about the radial axis which may make the motor ineffective or inefficient. The oscillating movement of the propeller blades can take place if the centre of gravity of the propeller blades is so positioned that the backlash in the gear train and the center of gravity can cause the propeller blade to shift slightly after being positioned at a particular pitch angle with respect to the radial axis.
In one preferred embodiment of the invention, the motor therefore further includes backlash preventing means for preventing movement of the propeller blade about the radial axis due to any backlash in the phase adjusting means so any backlash is not transmitted to the propeller blades which may otherwise cause the propeller blades to oscillate.
Preferably the backlash preventing means is provided in the coupling means for coupling each propeller blade to the second output shaft and includes:
a screw-thread section coupled to or provided on the second output shaft;
a yoke provided on the screw-threaded section for movement on the screw-threaded section in the longitudinal direction of the second output shaft; and
the engagement between the screw-threaded section and the yoke forms a substantially rigid coupling of the second output shaft to the propeller blades so that any backlash in the phase adjusting means is not transmitted through the coupling means to the propeller blades.
The prevention of any backlash being transmitted to the propeller blades occurs because of the screw-threaded nature of the backlash preventing means within the coupling means which does not allow any play or backlash in the drive train from the phase adjusting means, second output shaft and coupling means to the propeller blades.
In this embodiment of the invention, the coupling means further includes means for preventing rotation of the yoke on the screw-threaded section so that when the second output shaft is rotated relative to the first output shaft, the yoke is caused to move longitudinally on the screw-threaded section, the coupling means further having a link coupled between the yoke and the propeller blade so that when the yoke moves on the screw-threaded section, the link is moved to in turn cause the propeller blade to rotate about the radial axis to adjust the pitch of the blades relative to the radial axis.